Various types of force detection devices are used for controlling the motions of robots and industrial machines. Compact force detection devices are also incorporated as man-machine interfaces of input devices for electronic equipment. In order to achieve miniaturization and cost reduction, a force detection device that is used in such an application is required to be as simple in structure as possible and yet enable forces of the respective coordinate axes in three-dimensional space to be detected independent of each other.
Multi-axis force detection devices that are presently used can be classified into a type, with which specific directional components of a force that acts on a three-dimensional structure are detected as displacements that arise at a specific part, and a type, with which the directional components are detected as mechanical strains that arise at a specific part. A capacitance element type force detection device is a representative device of the former displacement detection type, and with this device, a capacitance element is comprised of a pair of electrodes and the displacement arising at one of the electrodes due to an acting force is detected based on the static capacitance value of the capacitance element. Such a static capacitance type force detection device is disclosed, for example, in Japanese Patent Publication No. 215627/1993. Meanwhile, a strain gauge type force detection device is a representative device of the latter strain detection type, and with this device, the mechanical strain that arises as a result of an acting force is detected as a change of gauge resistance or other form of electrical resistance. Such a strain gauge type force detection device is disclosed, for example, in Japanese Patent Publication No. 292029/1986.
In general, the objects of detection by a force detection device are force components in the direction of predetermined coordinate axes and moment components about the predetermined coordinate axes. In the case where an XYZ three-dimensional coordinate system is defined in three-dimensional space, the objects of detection will be the six components of the force components Fx, Fy, and Fz in the directions of the respective coordinate axes and the moment components Mx, My, and Mz about the respective coordinate axes. However priorly, regardless of the displacement detection type or the strain detection type, a force detection device of a considerably complex three-dimensional structure was required to detect the respective components independent of each other.
Thus an object of this invention is to provide a force detection device that can detect forces and moments in a distinguishing manner by means of a structure that is as simple as possible.